"My View on Coed Sleepovers", article about the paradoxes of gender-separation.
My father was one of those people, though liberal and laid-back, who could not imagine a man and a woman hanging out without sex on the menu.
Once, my sister, then in her twenties, had a male friend sleep over. There was no correcting my dad's assumption that they had had sex, so I guess nobody even tried. (I remember though this guy being apparently so hot that my sister said she had to leave the room when he stripped to his Speedos. :-)
When I was in twenties, I had an art exhibition in Copenhagen. My dad and his girlfriend came by. By nice coincidence, a lovely friend came by, on rollerskates and everything, and all were introduced, it was a nice afternoon. Later when talking to dad, it was clear that he took it for granted that she and I were an item. I did nothing to disabuse him of the idea.